Development of a Dynamic Pressure Response Calibrator
Abstract
Measurements of dynamic acoustic pressures in turbine and rocket engines are often made by separating the transducing element from the measurement point with tubing. The tubing is used for thermal isolation and/or when there are size constraints. The acoustic properties of the tubes require that the tubing and sensor unit be calibrated together as a system. A prototype calibration system has been designed and implemented which is capable of providing a controlled input pressure to the tubing and sensor pair. The specifications require input pressure spanning a frequency range of 2-500 Hz, a level of between 1 psi (171 dB re 0.0002 microbar) and 0.001 psi (100 dB), with tubing volumes as large as 10 cu.in. Input excitation is either swept-sine or random. The entire range of specifications was met for the swept-sine input (except the very lowest pressure setting). The random excitation input never met the specifications for the highest pressure range. The system utilizes a choice of driver configurations (high frequency compression driver or shaker and piston). The precise control of the input is achieved by careful design and sizing of the input cavity and placement of the reference sensor and a digital servo-controller. The design was carried out by a novel hybrid modelling technique using finite element models of the acoustic cavity and combining these with an admittance model of the driver.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1988
- Accession Number
- ADA239595
Entities
People
- Kevin E. Smith